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Hot Wire Your Car

From Wired How-To Wiki

Nine times out of ten, the term "hot-wire" summons images of car theft. Of course, anyone who's been stranded in a hostile environment without their car keys knows better. Here's the trick to getting your vehicle moving again.

Contents

What you'll need

Proof of ownership of the vehicle

Slotted screwdriver

Wire stripper

Insulated gloves

Try the screwdriver

It's not pretty, but a screwdriver can save you some trouble.

If you're considering hot-wiring your car, chances are you're already in dire straits. Before making things worse by removing the ignition cover and making a general mess of your vehicle, it might be worth trying the old "screwdriver in the ignition" trick. All this calls for is inserting a slotted screwdriver in the ignition and turning it over like a regular key. If the car starts, you've saved yourself the hassle and electrical hazards of hot-wiring.

No such luck? Don't fret. You'll still need the screwdriver for the following steps. Just be sure not to get it stuck in the ignition cylinder.

Remove the ignition cover

Be careful not to do permanent damage when removing the cover. Photo by exfordy on Flickr

Before continuing, be sure to exercise extreme caution. The following steps can result in painful electrical shocks, so follow the instructions carefully.

The first step is to gain access to the wiring. Most cars have large plastic panels that snap together and cover the top and bottom of the steering column. You'll want to carefully remove these panels so that the cylinder (and the wires running into it) are exposed. At some point you'll want to put these pieces back together, so be sure to use a feather touch while separating them.

Identify the battery and starter wires

You'll typically see three pairs of wires running into the back of the cylinder. Don't freak out -- each pair just represents a different key position on the ignition. In short, one pair should trigger the battery-only position, another pair the lights and radio position, etc. Of course, this also means one pair is responsible for the final key position -- starting the car.

Here's where it gets tricky. Everything you need is laid out in front of you, but there's no universal color system for the wires. Consulting your car's manual is probably the best way to find out your vehicle's specific color code. However, in a pinch the red pair is usually the set that provides power to the car, and the brown (which can be a single wire or a pair depending on the car) handles the starter.

Strip and connect the power wires

Once you've located the wires that provide power to the car, disconnect them from the cylinder. Use the wire stripper to remove the plastic from the ends and then twist them together. The fruits of your labor should be obvious -- power to the dashboard, lights, and pretty much everything else in the car.

Connect the starter wires to the power wires

Now things get dangerous. Although connecting the power wires is relatively safe, the wires responsible for starting the car carry live current. Under no circumstances should you touch the bare starter wires! With that in mind, strip the insulation off the ends of the wires and carefully touch them together. You should see a spark and hear the engine fire up. Once it's started idling, separate and cover the ends of the starter wires. They still pose an electrical hazard even after the vehicle has started, and you don't want them dangling around your knees.

TIP: This process may be slightly different for older cars. If you discover that the vehicle has a single starter wire (as opposed to a pair), you'll want to disconnect and handle the wire in the same fashion mentioned above. To start the car, the starter wire must come in contact with the connected power wires. Once the engine has started, remove the starter wire from the circuit and cover its exposed tip.

Things to consider

Hot-wiring is illegal if you don't own the car, so have your ID and registration (or some other proof of ownership) handy. If you are helping out a friend, that person must be able to prove ownership and must remain with you during the entire process.

Many cars have a mechanism that locks the steering wheel unless a key is in the ignition. So, even if you get the car started without a key, you may not be able to turn the steering wheel.

If you're not sure you know what you're doing, don't even start. You can do serious, hard-to-troubleshoot (in other words, expensive) damage to wiring and other components if you accidentally ground (or power) the wrong circuit.

Newer cars have a computer chip in the ignition system that requires a matching key. Most of them have an RFID chip that works when in proximity to the steering column. Without a key, these cars cannot be hot-wired. If your key does not turn the mechanical locks, simply taping it to the steering column may enable you to hot-wire the car.

Slightly older cars have resistors at very precise resistances (such as 11.7ohms) built in to the keys. These need to be matched with a value stored in the car's memory to start the car. After a few (typically 3) mismatched resistances, the ECU will lock out the ignition.

Note: As a rule of thumb you should not touch bare electrical wires, but in this case it won't do you any harm. The battery can provide hundreds of amps (known as cranking amps) to start the engine, but it supplies them at only 12V. A voltage that low can't push sufficient current through you to hurt (this is why you can hold 12V camera batteries in your bare hands without any problem) - This due to the "breakdown voltage" of skin, as is between 30v and 48v DC. But if your hands are wet, touching the wires is a very bad idea, as is applying the power beneath the skin (there is a story somewhere on the Web of someone sticking multimeter pins into his thumbs and electrocuting himself).

The real problem arises if you short the battery across a piece of metal. A battery can supply as much current as a welder, hence the story on the Web of a guy who was working on his car and dropped a spanner, shorting the battery to the car and welding his wedding ring to the chassis. Combined with the hydrogen gas generated, and you can have an explosive situation.

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